DVD Optical Head Research Articles

Low energy-density recording with a high-repetition-rate laser beam in gold-nanorod-embedded discs

In this paper, we report on the low energy-density recording with a high-repetition-rate femtosecond pulsed beam in homogenous gold-nanorod-dispersed discs by using low numerical aperture (NA) micro-optics. By focusing a femtosecond pulsed beam at a repetition rate of 82 MHz using a low NA DVD optical head, the spatially-stretched energy density introduces a temperature rising of the polymer matrix. This temperature rising facilitates the surface melting of gold nanorods, which leads to over one-order-of-magnitude reduction in the energy-density threshold for recording, compared with that by focusing single pulses through a high NA objective. Applying this finding, we demonstrate the dual-layer recording in gold-nanorod-dispersed discs with an equivalent capacity of 69 GB. Our results demonstrate the potential of ultra-high density three-dimensional optical memory with a low-cost and DVD-compatible apparatus.

Development of a low-cost microscope using a DVD optical pickup head

This paper presents a novel, low-cost microscope using the DVD optical pickup head (OPH) of an obsolete computer. This system utilizes two optical lenses in the DVD OPH, for easy adjustment of the magnification and focusing, as well as a retractable light path, which allows users to explore the fundamental components of microscopy. Performance analysis of the developed microscope presents magnification and resolution measurements of approximately 152 and 161lines/mm, respectively, when the ocular lens is located 20cm from the CCD.

Utilization of a digital-versatile-disc pickup head for benchtop laser microfabrication

Laser microfabrication is now offering interesting solutions to rapidly produce high-resolution photomasks or microstructures. However, most works require expensive commercial lasers and computer numerical control platforms, limiting its use by a large public. In this paper, we report the construction of a simple, custom-made, easily reproducible, automated laser system, based on a DVD optical pickup head. A user-friendly computer interface specifically designed to operate a motorized three-axis platform with micrometric precision controls focus distance and in-plane displacements. Writing performance characterization for both direct ablation and sintering of commercial black toner demonstrated flexibility in tridimensional microfabrication resolution and speed thanks to precise management of laser power and exposure time, with a minimal resolution of 3.1 μm.

An Astigmatic Detection System for Polymeric Cantilever-Based Sensors

We demonstrate the use of an astigmatic detection system (ADS) for resonance frequency identification of polymer microcantilever sensors. The ADS technology is based on a DVD optical head combined with an optical microscope (OM). The optical head has a signal bandwidth of 80 MHz, allowing thermal fluctuation measurements on cantilever beams with a subnanometer resolution. Furthermore, an external excitation can intensify the resonance amplitude, enhancing the signal- to-noise ratio. The full width at half maximum (FWHM) of the laser spot is 568 nm, which facilitates read-out on potentially submicrometer-sized cantilevers. The resonant frequency of SU-8 microcantilevers is measured by both thermal fluctuation and excited vibration measurement modes of the ADS.

Low-Cost Optical Measurement for Micro-Displacement with High Accuracy

Micro-displacement measurement with high accuracy plays a vital role in micro/nano manufacturing technology. In this paper, three low-cost techniques for micro-displacement measurement with high accuracy are discussed, and they are the methods based on DVD optical head, burred images and stop-action images. The techniques based on the DVD optical head and burred images are very attractive for many applications where the low cost is indispensable, and the method based on stop-action images has also better performance when measuring the static micro-displacement. Then, an application based on the stop-action images approach is given, and this method can measure the micro-displacement with nanometer accuracy. In addition, these discussions show that the methods based on the DVD optical head and burred images are a possible direction for low-cost micro-displacement measurement with high accuracy.

A hybrid scanning probe microscope (SPM) module based on a DVD optical head

The development of a highly sensitive (sub-nanometer) and multi-platform scanning probe microscope (SPM) module is presented. The module is based on an optical DVD pick-up head and uses its astigmatic detection scheme to detect the vertical displacement of the SPM cantilevers. The complete hybrid SPM module is capable of scanning in SPM intermittent contact, SPM contact and optical profilometry modes. The module can be used in a modified optical microscope or be implemented in a stand-alone system. Measurement results prove that the mechanical stability of this SPM module is high enough for atomic resolution imaging. Both scanning-sample and scanning-probe-type SPM setups have been tested based on this SPM module. The noise level and drift rate in the z-direction of the stand-alone system are 10 pm (rms) and 0.2 nm min−1, respectively.

Development of a low-cost nanoscale touch trigger probe based on two commercial DVD pick-up heads

This study develops a low-cost three-dimensional nanoscale touch trigger probe based on two commercially available DVD optical pick-up heads. The probe is attached to a cross-form structure suspended from a symmetrical arrangement of thin steel strips. The displacements of the probe tip in response to a contact force are initially investigated using a theoretical approach and are then confirmed using ANSYS finite element software. A touch trigger probe system is then constructed in accordance with the finite element simulation results, and a series of experimental investigations is performed to evaluate its performance characteristics. In general, the results show that the symmetrical suspension mechanism restricts the probe to three degrees of motional freedom, achieves an equal stiffness condition in every direction and reduces the pre-travel error. It is shown that the touch trigger probe has a pre-travel variation of less than 96 nm in all measurement directions and a unidirectional repeatability of 46 nm. Finally, the maximum triggering force is found to be less than 0.1 mN for any approach angle.

Two-dimensional optical accelerometer based on commercial DVD pick-up head

This study develops a low-cost, highly sensitive two-dimensional optical accelerometer based on a commercially available DVD optical pick-up head. Vibrations of the structure of interest cause a change in the angle of the seismic mass within the accelerometer. The relative movement between the seismic mass and the base produces a change in the distribution of a focused light spot on the surface of a four-quadrant photodetector. The resulting change in the output of the voltage signals by the photodetector is then used to calculate the corresponding acceleration of the base. The experimental results indicate that the resonant frequencies of the accelerometer in the X- and Y-axis directions are 92.75 Hz and 92.87 Hz, respectively. Furthermore, the useful frequency range of the accelerometer is found to be approximately 20% of its resonant frequency. The sensitivities of the accelerometer in the X- and Y-axis directions are 22.9 V/g and 21.3 V/g, respectively. Finally, the noise equivalent acceleration (NEA) of the accelerometer is found to be less than 30 µg Hz−1/2 over the frequency range 0.5–50 Hz.

Dynamic characterization of MEMS cantilevers in liquid environment using a low-cost optical system

Taking advantage of an off-the-shelf, high-quality but inexpensive optical detector, namely a DVD optical head, a system has been developed for the dynamic characterization of the vertical (out-of-plane) displacement of MEMS structures. The novelty of the proposed setup, besides the proposed field of application, lies in the ability of the system to operate both in air and in a liquid environment. In order to give a representative experimental proof of the functionality of the system, a cantilever array was designed and fabricated via a commercially available multi-user polysilicon surface micromachining process (PolyMUMPs). The frequency response of a tiny silicon cantilever beam (150 µm length, 10 µm width and 1.5 µm thickness) was measured, both in air and in deionized water, and compared against theoretical models of the system. Despite the low-cost signal conditioning system used, it was possible to trace a very clear Bode plot, and to obtain good agreement between experimental data and theoretical predictions. The measurements indicate that this displacement sensor performs very well under many circumstances of interest which require continuous monitoring with large bandwidth. This sensor offers a good low-cost measurement solution for the single-point dynamic characterization of the MEMS devices, particularly when the frequencies involved are high and the working environment is unsuitable for other types of detectors.

Design of miniature HD–DVD optical pick-up head using a Penta prism

A novel design of HD–DVD optical pick-up head is proposed. The geometrical size of the pick-up head is reduced by using a combined system of a Penta prism and an aspherical lens. Such a combined system can replace the mirror and collimating lens in a conventional pick-up head, to achieve a miniature HD–DVD pick-up head.

Servo Synthesis for an Optical Pick-up Head with Tilt Compensation

The new DVD optical heads are equipped with tilt control mechanism to compensate for the disk tilt. From the servo point of view, the tilt control shares the same push-pull tracking error (PPTE) signal from the optical head and are compensating the same control goal. In addition, the system exhibits highly nonlinear characteristics due to the change in the lens tilt. This study derives the optical head nonlinear dynamic model based on the Newtonian mechanics. The model indicates that the nonlinear effects mainly arise from the variation in the lens tilt. With reasonable approximations, it is possible to separate these nonlinear factors and lump them into a system variation term. The popular μ synthesis procedure is then used for the controller design.

Optical Head for CD & DVD.

Recent technological developments for CD and DVD optical heads are described. Optical heads play a key role in supporting optical disks, for which a large market has been formed. To evolve optical disks from playing only into recordable ones with a higher density and a larger capacity, high-power, high-resolution optical heads have been developed. The advent of a higher-performance optical head largely depends on the development of laser diode technology, as well as on the development of optical technology.

高速波面収差検出によるＤＶＤ光ヘッドアライメント

The objective lens for DVD optical-heads must have high optical performance, being aligned in high accuracy on the optical head For high speed of this alignment process, a method based on wave aberration included in exit light from the objective lens on the optical head has been studied. An optical system based on stable shearing interference with diffraction grating has been devised, as well as algorithm that can detect coma aberration from fringe patterns formed in this optical system. This algorithm processes divisional area of patterns therefore this algorithm can detect coma at high speed, besides independently of spherical aberration or astigmatism Alignment system of the objective lens on DVD optical head based on these optical system and algorithm has been developed. This system detects coma at 0.5s intervals and repeatability of tilt measurement is 0.01°. This alignment system has achieved high-accuracy alignment of 0.14° at 3 σ that is enough for DVD optical-heads, attaining 1/3 to 1/4 alignment time of conventional jitter method or spot method.

ＤＶＤ光ヘッドによる卓上型光造形装置と高分解硬化特性

A micro-photoforming whose unit laminated layer is made by a spinner is proposed. A high resolution of 2 μ m was confirmed to solidify a visible light curable resin using a DVD optical head. A 30 μ m diameter shuttlecock optical rotator was fabricated to indicate the possibility of 3D microstructures.